1. Field of the Invention
Aspects of the present invention relate to an apparatus and method for recording and/or reproducing holographic data, and more particularly, to an apparatus and method for recording and/or reproducing holographic data using a single side input method in which an optical structure is simplified.
2. Description of the Related Art
Recently, information storage technology using holograms has become more widely used. A holographic data storage method using holograms stores data in the form of an optical interference pattern in a polymer material or an inorganic crystal that is sensitive to light. The optical interference pattern is formed by using two laser beams exhibiting an interference feature. That is, the interference pattern is formed when a reference beam and a signal beam having different paths interfere with each other. This interference causes a chemical or physical change to a photosensitive storage medium, thereby recording data. In order to reproduce the data from the recorded interference pattern, a reproduction beam similar to the reference beam used for recording is emitted onto the interference pattern recorded on the storage medium. The reflected reproduction beam is diffracted due to the interference pattern so that the signal beam is restored and the data is reproduced.
Holographic data storing technology includes a volume holographic method and a micro-holographic method. The volume holographic method records and/or reproduces data in units of pages using volume holography, while the micro-holographic method records and/or reproduces data in units of single bits by using micro-holography. The volume holographic method has an advantage in that a large amount of data can be processed at the same time. However, the volume holographic method is difficult to commercialize as an information storage device to general consumers because an optical system therefor needs to be precisely adjusted.
In the micro-holographic method, two condensed light beams are made to interfere with each other at a focal point. By moving this interference pattern on a plane of a storage medium, a plurality of patterns are recorded to form an information plane. By piling up the information planes in a depth direction of the storage medium, information is recorded in a 3-dimensional (3D) manner.
A conventional micro-hologram type recording and/or reproducing apparatus includes an optical system for the signal beam and an optical system for the reference beam in order to emit the signal beam and the reference beam to both sides of the storage medium. These two optical systems result in a complicated recording and/or reproducing apparatus. Furthermore, since the signal beam and the reference beam must be focused in an area having a diameter of about 1 μm or less in order to form the interference pattern, each optical system needs to be aligned with high precision.